The present invention provides an assay for detecting the presence of an array or a profile of antioxidant activity in any sources or products.
When materials such as food are exposed to air, oxidative deterioration can occur. Oxidation can detrimentally effect the taste, color, and nutritional content of food. To prevent this deterioration, compounds that prevent oxidation, antioxidants, are added to food. Traditionally, the food industry has relied on antioxidants which are chemically synthesized. However, the possible toxicity of these compounds has stimulated the search for natural products with antioxidant properties. Similarly, a trend in the nutritional industry is to provide supplements providing antioxidant activity. These supplements are useful for eliminating free radicals that may contribute to aging or disease in mammals.
In the past, materials were screened for antioxidant activity using methods that determine the total antioxidant activity of all the antioxidants in the sample. For example, Yen and Duh, J Agric. Food Chem. 1994, 42:629-632, extracted peanut hulls with a polar solvent (methanol) and determined the total amount of antioxidant activity of all of the natural products contained in the extract. The ability of this mixture of compounds to scavenge each of a stable free radical, a peroxide, metals, superoxide, and hydroxyl radical was studied. However, their method was of limited use for two reasons. First, the antioxidant activity of all the natural products in the polar fraction are reported as a single total value. Unfortunately, from this report, one cannot ascertain the individual antioxidant activity of each natural product. Second, the antioxidant activity of the remaining fractions (the non-polar and semi-polar fractions) were not tested.
Similarly, others have also reported methods for determining the antioxidant activity of all the natural products in a sample. Kauffman, U.S. Pat. No. 5,239,258, describes a method in which a sample of material is dissolved and subjected to single sweep voltammetric analysis to measure the current through the sample as a function of the potential applied. The resulting current-voltage plot reflects the total level of oxidation products present in the material sampled. Davies, U.S. Pat. No. 5,427,951, describes a diagnostic test in which a sample is contacted with myoglobin and a compound which reacts to form a chromogenic species. Miller, U.S. Pat. No. 5,556,787, describes a method of determining the presence of oxidants or reductants in a sample using polyanilines as chromogenic agents. Porter, U.S. Pat. No. 4,253,848, describes a method for rapid, dry, non-destructive assay of the oxidative status of unsaturated lipids in whole foods, fats or oils by monitoring the fluorescence of compounds formed by the reaction of volatiles from oxidizing lipids and a polymerized xcex5-caprolactam. Like the method of Yen and Duh, the antioxidant activity of all the natural products in sample are reported as a single total value.
There is a need for a method that detects the antioxidant activity of individual antioxidants in a sample. Such a method would allow one to identify individual compounds with antioxidant activity, to monitor the stability of the antioxidant activity of individual components over time, and to compare the antioxidant profile of different samples.
The present invention provides a rapid and efficient method for identifying an antioxidant activity profile of a sample. Such a profile allows one to readily ascertain the total activity of the sample and to attribute antioxidant activity to individual components.